Window / RadWindow And MDI with ajax problem

I try this demo Window / RadWindow And MDI and this work good but in my case I have in my page an ajaxified grid when grid refresh with ajax, I can't see my radwindow when i click on tabstrip tab. If I check javascript function function OnClientTabSelected(sender, args)I have no error and my win object is not null but i don't see anything. Do you have an idea ? Possible problem with zindex calcul ?

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